No way of knowing until its growth habit, flowers and fruit become apparent in a few year's time.

If it is in a spot where it won't be in the way, I'd probably let it bloom and fruit. Even the wild crab apple species tend to be fairly ornamental, but I don't have much experience with seedlings of cultivars, which I'm betting yours is. It depends on whether you're willing to spend years watching it, just to decide it's worthless, lol. But there's a (small) chance that it could be a superior form. I will place this caveat: malus are highly susceptible to leaf diseases, and unless it shows good resistance, I wouldn't waste my time. A nearly leafless tree in August is not a pretty sight.

If you do decide to keep it, it needs to be moved to an open area.

tj

Thank you for the comments. Waiting for 2-3 years to find out, is not an option for me. :(

" Most things that self sow in your yard...are normally called WEEDS...and never forget that"

While I would not call them "weeds" necessarily, trees that self seed in your garden are rarely ones you want to encourage and very often pop up in inconvenient locations.

The only trees I encourage are preexisting or ones that I have planted myself.